Equilibrium slag losses in ferrovanadium production

Ferrovanadium is sometimes produced from V2O3 in electric are furnaces, usi ng aluminum as a reductant. The CaO fluxes the alumina, which forms during reduction of the vanadium oxide. Incomplete reduction of vanadium oxide fro m the slag is a significant cause of vanadium losses. To quantify factors t hat can affect the equilibrium vanadium loss, the vanadium oxide activity c oefficient was measured experimentally for different slag compositions. Hyd rogen-water mixtures were used to control the partial oxygen pressure (appr oximately 10(-13) atm) over CaO-Al2O3 slags contained in vanadium crucibles at 1700 degreesC; gas-phase mass transfer was controlled by jetting the ga s mixture onto the slag surface. Manipulation of the redox conditions at a single slag composition and temperature showed that, as expected, the vanad ium is present in the trivalent state in the slag. The slag basicity (CaO-A l2O3 ratio) was found to have a very strong effect on the activity coeffici ent of VO1.5, with clear implications for the effect of plant practice on v anadium loss.